The proposed training and research uses longitudinal and behavioral genetic approaches to investigate the causal link between internalizing symptoms (INT) and alcohol use problems (AUP; heavy alcohol use and alcohol use disorder; DSM-V, American Psychiatric Association, 2013) in men and women. Nationally- representative samples have confirmed high rates of comorbidity between INT and AUP and some evidence suggests that the INT-AUP association may be stronger in women. Despite their common co-occurrence, prior work has not fully characterized how these disorders interact during development in women compared with men. It remains unclear whether (1) INT predicts the onset of AUP symptoms (or vice versa), (2) a bidirectional relationship between INT and AUP is present, such that each increases risk for the other and exacerbates the other, and (3) INT and AUP are consequences of other general or common causes that contribute to each (e.g., genetics or shared environment). The proposed program of research seeks to provide evidence for how these disorders co-develop in men and women from childhood through adulthood and isolate the effects of INT on AUP over and above the influence of other possible common causes. Data for this project come from three, ongoing longitudinal studies: the Michigan Longitudinal Study (MLS), the Minnesota Twin and Family Study (MTFS), and the National Survey of Adolescent Health (AddHealth). Study 1 will model the co-development of INT and AUP from childhood through young adulthood using MLS data to determine if INT has a prospective effect on AUP in women compared with men. Study 2 will use the MTFS data to conduct discordant twin and propensity score analyses to develop causal inferences regarding the effects of INT on AUP (and vice versa) by controlling for unmeasured genetic and shared environmental influences that could be a common cause for both disorders. Study 3 will determine if these effects are replicable and generalize to a broad population of men and women using a nationally-representative prospective data set (AddHealth). The training component of the project is centered on two goals for the PI, Katherine Foster: (1) advance expertise in skills paramount for building an independent line of inquiry examining the etiological mechanisms of AUD with a focus on gender differences and (2) develop proficiency in research design, statistical analysis, and other technical skills requisite for addressing research question using sound methodology. The training will be accomplished over three years via a rigorous program of coursework in relevant analytic techniques, research collaboration and mentorship with preeminent scholars in the field of alcohol use research, and professional development in the area of scientific communication. Completion of the proposed training and research under an NRSA award would provide a vital foundation for Katherine's career as an independent research scientist.